When an AM resin company makes, for instance, a Sherman turret with raised bustle, cheek armor, and deleted pistol port, the guy isn't going to scratch build an entirely new turret. If it's for a Dragon kit, the guy will take the Dragon turret and scratch modify it for the master. I don't see how this much different than the figures. In both cases somebody is using somebody else's intellectual property for their own gain.
In a series of postings on Armorama several years ago, a 1/72 armor resin caster, who freely admitted using a modified Dragon kit as a master, wanted to sue another resin caster for using a modified version of his work for a further different version. Isn't this just a case of the "pot calling the kettle black"?

No not the same, a Sherman turrent has a dimension/s so they are going to be, look the same, using a leg of someones figure with the same creases is totally different. Sculpting a leg to look real is an art and takes time( so does a Sherman don't get me wrong). Not trying to start something but I personally think promotion of this type of work is wrong.
The Sherman debate

CMK has obviously taken the old saying "good artists borrow, great artists steal" to heart.

But CMK is only at the point of borrowing, not stealing. Because the whole point of stealing is to do it so well no one ever catches you. That's what makes an artist who steals great.